Daylight sensor having a rotatable enclosure

ABSTRACT

A daylight sensor is adapted to be mounted to a surface in a space having a window, and has a rotatable enclosure for directing a lens of the daylight sensor towards the window. The daylight sensor includes a photosensitive circuit for measuring a light intensity in the space, and an enclosure for housing the photosensitive circuit. The lens directs light from the space towards the photosensitive circuit. The enclosure has a cover portion and a base portion adapted to be mounted to the surface. The cover portion is rotatable with respect to the base portion, so as to direct the lens towards the window after the base portion is mounted to the surface. The base portion may also include a cylindrical wall having a channel adapted to capture a snap of the cover portion, such that the snap may move angularly through the channel to allow for rotation of the cover portion with respect to the base portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application of commonly-assignedU.S. Provisional Application Ser. No. 61/285,691, filed Dec. 11, 2009,entitled DAYLIGHT SENSOR HAVING A ROTATABLE ENCLOSURE, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to daylight sensors for determining theambient (i.e., total) light level in a space, and more particularly, toa daylight sensor having a rotatable enclosure for easily directing alens of the daylight sensor towards a window.

2. Description of the Related Art

Many rooms in both residential and commercial buildings are illuminatedby both artificial light from a lighting load, such as an incandescentlamp or a fluorescent lamp, and daylight (i.e., sunlight) shiningthrough a window. Daylight sensors (i.e., photosensors) are often usedto measure the total light level in a space in order to adjust the lightintensity of the lighting load to thus adjust the total light level inthe space. For example, the light intensity of the lighting load may bedecreased as the daylight level increases (and vice versa), so as tomaintain the total light level in the space approximately constant. Adaylight sensor typically comprises a lens for directing the light inthe space towards an internal photodetector (such as a photodiode) formeasuring the total light level in the space. Daylight sensors aretypically mounted to a ceiling in the space at a distance from thewindow. The lens of the daylight sensor must be positioned such that thefield of view of the daylight sensor is directed towards the window.Therefore, there is a need for a daylight sensor that may easily bemounted such that the lens is directed towards a window in a space.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a daylight sensoris adapted to be mounted to a surface in a space having a window, andcomprises a rotatable enclosure for directing a lens of the daylightsensor towards the window. The sensor further comprises a photosensitivecircuit for measuring a total light intensity in the space, and anenclosure for housing the photosensitive circuit. The enclosurecomprises a cover portion in which the lens is provided and a baseportion adapted to be mounted to the surface. The lens is operable todirect light from the space towards the photosensitive circuit. Thecover portion is rotatable with respect to the base portion, so as toallow the lens to be directed towards the window after the base portionis mounted to the surface.

According to another embodiment of the present invention, an enclosurefor a sensor is adapted to be mounted to a surface in a space having awindow, and comprises a base portion and cover portion that may berotated with respect to the base portion. The base portion has a rearsurface adapted to be mounted to the surface and a cylindrical wallconnected to the rear surface. A channel is formed in the cylindricalwall adjacent to the rear surface of the base portion. The cover portioncomprise a lens for receiving light from the space, and at least onesnap, which is captured in the channel of the base portion and isoperable to move angularly through the channel of the base portion toallow for rotation of the cover portion with respect to the baseportion, so as to allow the lens to be directed towards the window afterthe base portion is mounted to the surface.

Other features and advantages of the present invention will becomeapparent from the following description of the invention that refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simple diagram of a radio-frequency (RF) lighting controlsystem comprising a dimmer switch and a daylight sensor;

FIG. 2 is a simplified diagram of a room in which the daylight sensor ofFIG. 1 may be mounted;

FIG. 3A is a perspective view of the daylight sensor of FIG. 1 showing acover portion attached to a base portion of the daylight sensor;

FIG. 3B is a front view of the daylight sensor of FIG. 3A;

FIG. 4A is a top perspective view of the daylight sensor of FIG. 3Ashowing the cover portion detached from the base portion;

FIG. 4B is a bottom perspective view of the daylight sensor of FIG. 3Ashowing the cover portion detached from the base portion;

FIG. 5 is a left side cross-sectional view of the daylight sensor ofFIG. 3A taken through the center of the daylight sensor with the coverportion attached to the base portion; and

FIG. 6 is a rear perspective cross-sectional view of the daylight sensorof FIG. 3A with the cover portion attached to the base portion.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description ofthe preferred embodiments, is better understood when read in conjunctionwith the appended drawings. For the purposes of illustrating theinvention, there is shown in the drawings an embodiment that ispresently preferred, in which like numerals represent similar partsthroughout the several views of the drawings, it being understood,however, that the invention is not limited to the specific methods andinstrumentalities disclosed.

FIG. 1 is a simple diagram of a radio-frequency (RF) lighting controlsystem 100 comprising a dimmer switch 110 and a daylight sensor 120. Thedimmer switch 110 is adapted to be coupled in series electricalconnection between an alternating-current (AC) power source 102 and alighting load 104 for controlling the amount of power delivered to thelighting load. The dimmer switch 110 may be wall-mounted in a standardelectrical wallbox. Alternatively, the dimmer switch 110 could beimplemented as a table-top load control device. The dimmer switch 110comprises a faceplate 112 and a bezel 113 received in an opening of thefaceplate. The dimmer switch 110 further comprises a control actuator114 and an intensity adjustment actuator 116. Actuations of the controlactuator 114 toggle, i.e., turn off and on, the lighting load 104.Actuations of an upper portion 116A or a lower portion 116B of theintensity adjustment actuator 116 respectively increase or decrease theamount of power delivered to the lighting load 104 and thus increase ordecrease the intensity of the lighting load 104 from a minimum intensity(e.g., 1%) to a maximum intensity (e.g., 100%). A plurality of visualindicators 118, e.g., light-emitting diodes (LEDs), are arranged in alinear array on the left side of the bezel 113. The visual indicators118 are illuminated to provide feedback of the intensity of the lightingload 104. An example of a dimmer switch is described in greater detailin U.S. Pat. No. 5,248,919, issued Sep. 29, 1993, entitled LIGHTINGCONTROL DEVICE, the entire disclosure of which is hereby incorporated byreference. Alternatively, the lighting control system 100 could simplycomprise an electronic switch for toggling the lighting load 104 on andoff (rather than the dimmer switch 110).

The daylight sensor 120 is mounted such that the daylight sensor isoperable to measure a total light level L_(TOT) in the vicinity of(i.e., a space around) the lighting load 104 controlled by the dimmerswitch 110. The daylight sensor 120 includes an internal photosensitivecircuit, e.g., a photosensitive diode 125 (FIG. 5), which is housed inan enclosure 122 having a cover portion 124 and a base portion 126. Theenclosure 122 comprises a lens 128, which is provided in a front surfaceof the cover portion 124 and conducts light from outside the daylightsensor towards the internal photosensitive diode 125. The daylightsensor 120 is responsive to the total light intensity L_(TOT) measuredby the internal photosensitive diode 125. Specifically, the daylightsensor 120 wirelessly transmits digital messages to the dimmer switch110 via RF signals 106 in response to the total light intensity L_(TOT),such that the dimmer switch 110 controls the intensity of the lightingload 104 (and thus the total lighting intensity L_(TOT) in the spacearound the lighting load).

During a setup procedure of the RF lighting control system 100, thedimmer switch 110 may be assigned to (i.e., associated with) thedaylight sensor 120. The daylight sensor 120 transmits digital messageswirelessly via the RF signals 106 to the dimmer switch 110 in responseto the total lighting intensity L_(TOT) in the space. A digital messagetransmitted by the daylight sensor 120 includes, for example,identifying information, such as, a serial number (i.e., a uniqueidentifier) associated with the daylight sensor. The dimmer switch 110is responsive to messages containing the serial numbers of the daylightsensor 120 to which the dimmer switch is assigned. Each digital messagemay further comprise the measured total lighting intensity L_(TOT) inthe space. Accordingly, the dimmer switch 110 controls the intensity ofthe lighting load 104 to the new lighting intensity L_(NEW) in responseto receiving from the daylight sensor 120 a digital message with themeasured total lighting intensity L_(TOT) in the space. Alternatively,the digital messages could comprise a command, such as a specific newlighting intensity L_(NEW) for the lighting load 104. The operation ofthe RF lighting control system 100 is described in greater detail incommonly-assigned U.S. patent application Ser. No. 12/727,956, filedMar. 19, 2010, entitled WIRELESS BATTERY-POWERED DAYLIGHT SENSOR, theentire disclosure of which is hereby incorporated by reference.

FIG. 2 is a simplified diagram of an example room 130 in which thedaylight sensor 120 may be mounted. As shown in FIG. 2, the daylightsensor 120 is mounted to a ceiling 132 of the room 130 at a distancefrom a window 134 through which natural light (i.e., daylight) shines.In the example room 130 of FIG. 2, the lighting load 104 is also mountedto the ceiling 132 of the room 130, but may be mounted to other surfacesin the room. The room 130 also contains a task surface 136 (e.g., atable), which is illuminated by the natural light shining through thewindow 134 and the artificial light generated by the lighting load 104.The daylight sensor 120 is operable to measure the total light levelL_(TOT), which is a combination of the natural light and the artificiallight in the room 130. The natural light and the artificial light thatshine onto the task surface 136 are reflected to the daylight sensor120. In addition, natural light from the window 134 may shine directlyonto the daylight sensor 120. While not shown in FIG. 2, the room 130may comprise additional windows on different walls (i.e., on differentfaçades of the building, such as in a corner office). Accordingly, thelighting control system 100 may comprise multiple daylight sensors 120facing the multiple windows in the space. The dimmer switch 110 couldaverage the measured total lighting intensities L_(TOT) received fromthe multiple daylight sensors 120 in order to control the lighting load104.

According to the present invention, the enclosure 122 of the daylightsensor 120 comprises a rotatable enclosure, which allows the lens 128 tobe easily directed towards the window 134 after the daylight sensor ismounted to the ceiling 132 (or other surface in the room 130), such thatmore natural light than artificial light shines through the lens 128onto the internal photosensitive diode 125. In addition, since theenclosure 122 is rotatable, the lens 128 may be repositioned to bedirected in a different direction, for example, after an adjustment tothe layout of the furniture or walls in the room 130.

Since the light intensity of the reflected light shining on the daylightsensor 120 is less than the light intensity of the light shiningdirectly on the task surface 136, the daylight sensor is characterizedby a gain, which is representative of the difference between the lightintensity at the daylight sensor and at the task surface and may bestored a memory or the dimmer switch. The dimmer switch 110 uses thegain to attempt to control the illuminance (i.e., the light intensity)on the task surface 136 to a desired light intensity L_(SP) (i.e., asetpoint) in response to the measured total lighting intensity L_(TOT)in the space (as transmitted by the daylight sensor 120). Alternatively,the gain could be stored in a memory of the daylight sensor 120, forexample, if the digital messages transmitted by the daylight sensorcomprise command for the dimmer switch 110 to control the lighting load104 to new lighting intensities L_(NEW). The gain may be set during acalibration procedure, an example of which is described incommonly-assigned U.S. patent application Ser. No. 12/727,923, filedMar. 19, 2010, entitled METHOD OF CALIBRATING A DAYLIGHT SENSOR, theentire disclosure of which is hereby incorporated by reference.

FIG. 3A is a perspective view and FIG. 3B is a front view of thedaylight sensor 120. The lens 128 is transparent such that the lightfrom the room 130 is able to shine onto the internal photosensitivediode 125 of the daylight sensor 120. After the daylight sensor 120 ismounted to the ceiling 132, the enclosure 122 of the daylight sensor maybe rotated such that an arrow 140 points towards (and the lens 128 isdirected towards) the window 134. As a result, more natural light thanartificial light will shine through the lens 128 and onto the internalphotosensitive diode 125. A plurality of actuators (e.g., a calibrationbutton 142, a test button 144, and a link button 146) are used duringthe setup and calibration procedures of the daylight sensor 120. Thedaylight sensor 120 further comprises a laser-pointer receiving opening148, which is adapted to receive energy from a laser pointer (notshown). The daylight sensor 120 is responsive to the energy of the laserpointer shining through the laser-pointer receiving opening 148. Whenthe daylight sensor 120 is mounted to the ceiling 132, a user may shinethe laser pointer through the opening 148 rather than actuating thecalibration button 142 during the calibration procedure.

FIG. 4A is a top perspective view and FIG. 4B is a bottom perspectiveview of the daylight sensor 120 showing the cover portion 124 detachedfrom the base portion 126. FIG. 5 is a left side cross-sectional view ofthe daylight sensor 120 taken through the center of the daylight sensoras shown in FIG. 3B. FIG. 6 is a rear perspective cross-sectional viewof the daylight sensor 120 taken through the line shown in FIG. 5. Thecircuitry of the daylight sensor 120 is mounted on a printed circuitboard (PCB) 150, which is connected to the cover portion 124, e.g.,heat-staked via at least one stake 152 (FIG. 5). The daylight sensor 120comprises a battery V1 for powering the circuitry of the daylight sensor120. The circuitry of the daylight sensor 120 is described in greaterdetail in previously-referenced U.S. patent application Ser. No.12/727,956.

The cover portion 124 is mechanically connected to a battery holderstructure 154 for housing the battery V1. When received in the batteryholder structure 154, the battery V1 is electrically connected to thePCB 150 via electrical contacts 156, 158. The battery holder structure154 is mechanically connected to the cover portion 124. The batteryholder structure 154 comprises snaps 160, which are adapted to bereceived by tabs 162 on a cylindrical wall 164 of the base portion 126to couple the cover portion 124 to the base portion. The base portion126 comprises a rear surface 165 that is connected to the cylindricalwall 164. The rear surface 165 has a groove 166 for receiving a mountingstructure (not shown) that extends through openings in the rear surface165 and allows the daylight sensor 120 to be releasably be attached to amounting surface, such as a drop ceiling panel. An example of themounting structure is described in greater detail in U.S. patentapplication Ser. No. 12/371,027, filed Feb. 13, 2009, entitled METHODAND APPARATUS FOR CONFIGURING A WIRELESS SENSOR, the entire disclosureof which is hereby incorporated by reference. Alternatively, thedaylight sensor 120 could be attached to the mounting surface using, forexample, an adhesive (e.g., double-sided tape) or a screw receivedthrough a screw hole 167.

As previously mentioned, the enclosure 122 of the daylight sensor 120comprises a rotatable enclosure. The tabs 162 surround the circumferenceof the base portion 126 with only small gaps 168 between adjacent tabs,such that a channel 169 is formed between the tabs and the rear surface165 of the base portion. When the cover portion 124 is connected to thebase portion 126, the snaps 160 are each captured in the channel 169adjacent the rear surface 165 of the base portion. The width W_(SNAP) ofeach snap 160 (i.e., in the angular direction as shown in FIG. 4A) islarger than the width W_(GAP) of the gaps 168 between the adjacent tabs162, such that the snaps are held in the channel 169. The snaps 160 areable to move angularly through the channel 169 formed between the tabs162 and the rear surface 165, such that the cover portion 124 may befully rotated (i.e., rotated 360°) with respect to the base portion 126.The height of each snap 160 is sized such that the snap fits securelybetween the tabs 162 and the rear surface 165 while still allowing thecover portion 124 to rotate. Thus, after the base portion 126 isattached to the mounting surface and the cover portion 124 is attachedto the base portion, the cover portion may be rotated to direct the lens128 towards the window 134. Alternatively, the tabs 162 could all beconnected together (i.e., without the gaps 168 between the adjacenttabs).

The battery holder structure 154 further comprises two posts 170 thatextend towards the cylindrical wall 164 of the base portion 126. Thetabs 162 of the base portion 126 each have two parallel extensions 172forming detents 174. The posts 170 of the battery holder structure 154are received in the detents 174. The two posts 170 are located on thebattery holder structure 154 with respect to each other such that onepost is received in one of the detents 174 of the tabs 162 and the otherpost is received in one of the gaps 168 between the adjacent tabs 162(when the cover portion 124 is not being rotated with respect to thebase portion 126). The posts 170 and the detents 174 allow the coverportion 124 to be rotated to a plurality of discrete positions (ratherthan being continuously variable). The detents 174 are sized so as tofirmly hold the received post 170 in place, such that the lens 128 ofthe daylight sensor 120 is maintained in position directed toward thewindow 134. The gaps 168 formed between the adjacent tabs 162 are largerthan the size of the detents and do not function to hold the posts inplace. Alternatively, the detents 174 could be provided in the batteryholder structure 124 connected to the cover portion 124, and the posts170 could extend inwardly from the cylindrical wall 164 of the baseportion 126.

The cover portion 124 may be removed from the base portion 126 by simplypulling the cover portion away from the base portion. Removal of thecover portion 124 from the base portion 126 allows for replacement ofthe battery V1 in the battery holder structure 154. When the coverportion 124 is pulled away from the base portion 126, the snaps 160 ofthe battery holder structure 154 flex inwards (i.e., towards the batteryV1) and move past the tabs 162, such that the snaps are no longer heldin the channel 169. The cover portion 124 may be re-installed on thebase portion 126 by forcing the cover portion towards the base portion,such that the snaps 160 are once again received in the channel 169.

The present invention has been described with reference to the daylightsensor 120 for measuring the total light level L_(TOT) in the room 130.However, the concepts of the present invention can also be other typescircular control devices, such as, for example, ceiling-mountedoccupancy sensors, vacancy sensors, and temperature sensors. Inaddition, even though the present invention has been described withreference to the dimmer switch 110 for controlling the intensity of thelighting load 104, the concepts of the present invention could beapplied to load control systems comprising other types of load controldevices, such as, for example, electronic switches for togglingelectrical loads on and off, electronic dimming ballasts for fluorescentloads, and drivers for light-emitting diodes (LEDs). Additionally, theconcepts of the present invention could be used to control other typesof electrical loads, such as, for example, fan motors or motorizedwindow treatments. Examples of load control systems including othertypes of electrical loads, load control devices, and sensors aredescribed in greater detail in U.S. patent application Ser. No.12/845,016, filed Jul. 28, 2010, entitled LOAD CONTROL SYSTEM HAVING ANENERGY SAVINGS MODE, the entire disclosure of which is herebyincorporated by reference.

Lighting control systems including wired daylight sensors (i.e., wiredphotosensors) are described in greater detail in U.S. Pat. No.7,111,952, issued Sep. 26, 2006, entitled SYSTEM TO CONTROL DAYLIGHT ANDARTIFICIAL ILLUMINATION AND SUN GLARE IN A SPACE, and U.S. Pat. No.7,369,060, issued May 6, 2008, entitled DISTRIBUTED INTELLIGENCE BALLASTSYSTEM AND EXTENDED LIGHTING CONTROL PROTOCOL, the entire disclosures ofwhich are hereby incorporated by reference. Examples of other RFlighting control systems are described in greater detail in U.S. patentapplication Ser. No. 12/033,223, filed Feb. 19, 2008, entitledCOMMUNICATION PROTOCOL FOR A RADIO-FREQUENCY LOAD CONTROL SYSTEM, andU.S. patent application Ser. No. 12/203,518, filed Sep. 3, 2008,entitled RADIO-FREQUENCY LIGHTING CONTROL SYSTEM WITH OCCUPANCY SENSING,the entire disclosures of which are hereby incorporated by reference.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

What is claimed is:
 1. A daylight sensor adapted to be mounted to asurface in a space having a window, the sensor comprising: aphotosensitive circuit for measuring a light intensity in the space; anenclosure for housing the photosensitive circuit, the enclosurecomprising a cover portion and a base portion adapted to be mounted tothe surface, the cover portion having a lens operable to direct lightfrom the space towards the photosensitive circuit, the base portioncomprising a rear surface and a cylindrical wall connected to the rearsurface, the wall having a channel formed therein adjacent to the rearsurface, the channel formed by a plurality of tabs on the wallsurrounding a circumference of the base portion, the channel having gapsformed between the tabs, the cover portion comprising at least one snapcaptured in the channel and configured to move angularly through thechannel to allow for rotation of the cover portion with respect to thebase portion; wherein the cover portion comprises a structure having apost extending towards the cylindrical wall of the base portion, thepost configured to be received in detents formed in each of the tabs ofthe base portion to allow for rotation of the cover portion with respectto the base portion to a plurality of discrete positions, so as to allowthe lens to be directed towards the window after the base portion ismounted to the surface.
 2. The sensor of claim 1, wherein the structurecomprises a second post extending towards the cylindrical wall of thebase portion, the second post also adapted to be received in the detentsformed in each of the tabs of the base portion.
 3. The sensor of claim2, wherein, when one post is received in one of the detents, the otherpost is received in one of the gaps formed between the tabs.
 4. Thesensor of claim 1, wherein the structure is adapted to hold a battery ofthe sensor, the photosensitive circuit adapted to be powered by thebattery.
 5. The sensor of claim 1, wherein the snap of the cover portionis formed as part of the structure.
 6. The sensor of claim 1, whereinthe detents are formed by two parallel extensions of the tabs on thecylindrical wall of the base portion.
 7. The sensor of claim 1, whereinthe cover portion comprises a plurality of snaps adapted to be receivedin the channel of the base portion.
 8. The sensor of claim 1, wherein awidth of the snap in the angular direction is larger than a width of thegaps between the tabs.
 9. The sensor of claim 1, wherein the coverportion is configured to be fully rotated with respect to the baseportion.
 10. A daylight sensor adapted to be mounted to a surface in aspace having a window, the sensor comprising: a photosensitive circuitfor measuring a light intensity in the space; an enclosure for housingthe photosensitive circuit, the enclosure comprising a cover portion anda base portion adapted to be mounted to the surface, the cover portionhaving a lens operable to direct light from the space towards thephotosensitive circuit, the base portion comprising a rear surface and acylindrical wall connected to the rear surface, the wall having achannel formed therein adjacent to the rear surface, the channel formedby a plurality of tabs on the wall surrounding a circumference of thebase portion, the channel having gaps formed between the tabs, the coverportion comprising at least one snap captured in the channel andconfigured to move angularly through the channel to allow for rotationof the cover portion with respect to the base portion; wherein the coverportion comprises a structure defining a plurality of detents, the baseportion comprising a post extending from the cylindrical wall, the postadapted to be received in the detents of the structure of the coverportion to allow for rotation of the cover portion with respect to thebase portion to a plurality of discrete positions, so as to allow thelens to be directed towards the window after the base portion is mountedto the surface.
 11. An enclosure for a sensor adapted to be mounted to asurface in a space having a window, the enclosure comprising: a baseportion comprising a rear surface adapted to be mounted to the surfaceand a cylindrical wall connected to the rear surface, the cylindricalwall having a channel formed therein adjacent to the rear surface, thechannel formed by a plurality of tabs on the cylindrical wallsurrounding a circumference of the base portion with gaps formed betweenthe tabs; and a cover portion having a lens for receiving light from thespace, the cover portion comprising at least one snap captured in thechannel and operable to move angularly through the channel to allow forrotation of the cover portion with respect to the base portion to aplurality of discrete positions, so as to allow the lens to be directedtowards the window after the base portion is mounted to the surface;wherein the cover portion comprises a structure having a post extendingtowards the cylindrical wall of the base portion, the post adapted to bereceived in detents formed in each of the tabs of the base portion toallow for rotation of the cover portion to the plurality of discretepositions.
 12. The enclosure of claim 11, wherein the snap of the coverportion is formed as part of the structure, and the structure is adaptedto hold a battery of the sensor.
 13. The enclosure of claim 11, whereinthe cover portion comprises a plurality of snaps adapted to be receivedin the channel of the base portion.
 14. The enclosure of claim 11,wherein a width of the snap in the angular direction is larger than awidth of the gaps between the tabs.
 15. The enclosure of claim 11,wherein the cover portion is configured to be fully rotated with respectto the base portion.